Effects of transcranial magnetic stimulation (TMS) of rostral cingulate zone on social conformity

Recently we showed (Klucharev et al., 2009), using functional magnetic
resonance imaging, that social conformity is based on mechanisms that comply
with principles of reinforcement learning. Here we hypothesize that
transcranial magnetic stimulation (TMS) of the rostral cingulate zone - RCZ
(involved in reinforcement learning) could modulate the conformal behavioral
adjustments.

Primary Objective: Current project will study effects of TMS of the RCZ on
social conformity. A modulation the conformal behavior by TMS (Studies N 1&3)
would indicate the essential role of RCZ in social influence.
Secondary Objective(s): Additionally (Study N2) we will check is the role of
RCZ in conformity transient and limited to the time of the social conflict
between subject and group opinion.

To test our hypothesis, we designed a paradigm in which subject*s initial
judgments of facial attractiveness are open to influence by group opinion.
In the Study N1 we will show that 40-190 sec of off-line TMS of the RCZ will
change subjects* susceptibility for social conformity as compared to TMS of the
control area. In the Study N2 we will demonstrate that online TMS (2 sec) of
the RCZ applied at the different time-windows of the trials will have
differential effects on conforming behavior. In the Study N3 we hypothesize
that excitatory and inhibitory TMS of the RCZ will have opposite effects on
conforming behavioral adjustments.

Subjects* rostral cingulate zone (RCZ) or precuneus (control site) will be
stimulated by the figure-eight TMS coil (Magstim Super Rapid, Magstim Co.,
Whitland, Dyfed, UK) using the BrainSight Frameless Stereotactic System (Rogue
Research, Montreal, Canada).
A standard short version of TMS will be used for off-line stimulation (Study
N1&3), i.e. thetaburst stimulation (TBS) (Di Lazzaro et al., 2005; Huang et
al., 2005). Two standard protocols will be used: the intermittent theta burst
stimulation pattern (iTBS), a 2 s train of TBS is repeated every 10 s for a
total of 190 s (600 pulses) or cTBS - the continuous theta burst stimulation
paradigm, a 40 s train of uninterrupted TBS is given (600pulses) (for details
see (Huang et al., 2005)).
The online continuous TMS stimulation (Study N2) will consist of a 2 seconds
biphasic pulse train at 10Hz (for similar protocol see (Rushworth et al.,
2002). The TMS intensity will be set to: in Study N1&3 to of 80% Active motor
threshold (AMT) and in Study N2 to 110% AMT. All protocols follow safety TMS
guidelines (Anderson et al., 2006; Wassermann, 1998).

TMS is not painful at the level of intensity used at the project. From the
previous literature we know that some subjects could report a (light) headache.
Paracetamol is sufficient to treat these symptoms. On In the current
investigation we use stimulation parameters strictly within the aforementioned
guidelines. All subjects will be prescreened for relevant medical history. All
participants will give a written informed consent according to the Declaration
of Helsinki. All subjects will be explicitly informed that they could stop
their participation at any time without having to give any explanation.
Furthermore during all studies will be conducted in contact with a physician
(Prof. Dr. Jan Buitelaar, Department of Psychiatry, Radboud University Nijmegen
Medical Centre) for the treating of a possible epileptic attack.

Better understanding of reinforcement learning mechanisms brings new
perspective in the treatment of various behavioral disorders (e.g. treatment of
compulsive behaviors or development of an effective behavioral therapy). Social
conformity is one of the fundamental psychological phenomena underlings social
influence (Asch, 1951). Understanding of social conformity together with group
norms are important for an effective control of obesity, criminal behavior,
teenage alcohol abuse, and even for pro-environmental behavior (Cialdini and
Goldstein, 2004; Keizer et al., 2008). Overall, the topic of the study is
scientifically and socially important.